Not sure if that applies to outdoor but with my indoor grow the big fan leaves yellowed and fell off pretty quickly(at such rate that it got me worried sick), plants still finished well with the final product being amazing. I was told here by many folks that its normal process, the plant is simply "eating whats stored in the leaves ", but I was also told not to pick em off but to let them fall on their own. I only picked off those that didnt and got like really dry.